Sized, filled paper manufacture



United States Patent The present invention relates to the manufacture of sized, filled paper of improved weight and. opacity the beater addition process. The invention includes a dissolved sulfate ions up toaboutISO parts per million takes place.

' From the foregoing, it will be apparent that in closed 'or substantially closed white water systems the dissolved 1 sulfate ion content rises continuously Ta thefwaterjisf recycled, and values ashigh as: 1600parts per "million have been observed "in 7 actual mill 'opera'tions pared with this increase, the influence of dis'solvedfsodium ionsisniinor in'ipresentday.operations. r

method for utilizing thedissolved sulfate ion content :Oli paper mill white water systems whileproducing rosinsized paper and rosin-sizedwet strength paper containing barium sulfate and aluminum hydrate as fillers. The

invention further includes a method forextending the useful life of water in paper mills having closed or substantially closed white water systems, that-is, systems in which more than about- 60 %-80% 'of thvbwhitewater is recycled, by inhibiting the increase in the. dissolved A recent development of 'the paper industryiis' .the it manufacture of rosin-sized" wet strength. paperl iThe process followed is that outlined; above, except: that .a separately-prepared aqueous dispersion of a wet 'st'rengthfi .esin in cellulose-substantive form is added to the. fibrous suspension at an appropriate'point, usually justahead of the'headbox.v Thereafter the: suspension is' sheeted fin" normal manner and is heated and dried to curetheiesin on the fibers', thus'developing the-,strengthening propsulfate ion content of the water which normally takes place upon addition of alum. J V Cnstomarily, sized wet strength paper is manufactured by forming a diluteaqueous suspension of papermaking cellulosic fibers at a consistency of about /2-% l%, adding liquid resin or other soap size thereto, precipitating the sizing material on the fibers by the addition of alum,

adding a wet strength resin which is substantively ad-f sorbed by the fibers, and sheeting the fibers on a wire screen. The water employed to suspend thefibers drains through the screen and the cellulosic web on the screen is heated to dry the same and develop the wet strength of paper, paper of the resin therein with formation board, etc.

So far as is practical, the Water draining through the screen is recycled to form a fresh suspension of cellulosic fibers. It is found, however, that as the water is recycled it accumulates sulfate ions rapidly and vthat it further accumulates aluminum ions at a somewhat slower rate,

resulting principally from two inherent characteristics of 1 the rosin sizing process. In the first place, the theo'- retical equation for the reaction between rosinsize (as sodium rosinate) and alum (aluminum sulfate) calls for complete reaction between the aluminum sulfate and the rosin with formation of aluminum trirosinate which'pre cipitates, and sodium sulfate which remains in solution.

Thus, according to the equation, all of the aluminum is insolubilized while all of the sulfateions remain dissolved. The water also accumulates dissolved sodium ions, but at a still slower rate. t

The second cause of residual dissolved sulfate ions is the fact that in commercial practice the amount of alum found necessary to effect eflicient deposition of the rosin size and formation of v good quality paper is about. 150% of the weight of the rosin size. Since .the weight of t :alum theoretically necessary to precipitate rosin size is only about 33% of the weight of the rosin size, it is evident that a great excess of alum is added, this excess accounting for the largest part of the dissolved sulfate ions remaining and also accounting for the dissolved aluminum ions remaining after the size has set on'the fibers.

The minimum amount of. rosin size employed in the manufacture of sized paper is ordinarily about /2% based on the dry weight of the fibers, and to precipitate this size and form good quality paper, the presence of at least of alum is required. Addition of this amount of alum, however, causes the dissolved sulfate ion content of the water at 1% consistency, to rise up to about 38 parts per million depending principally onthe type of fibers employed and the pH of the. suspension. It is common to manufacture sized paper by the use of. much larger amounts of rosin size, for example, 2% of size and 3% of alum, and in such case an increase in the .erties of the resin thereon. 1 l 1 a 1 It is knownthatanumber of, wet strength resins are, I inactivated I or otherwise?renderedgless efiicient 'byj' the presence of too highortoo lowacontent, of" dissolved l ,sulfate ions in the water, and these include the widelyusedcationic melamineformaldehyde resins (cf. Maxwell et al.. U. S. Patent No. 2,559,221) and certain o'f; the

. anionic urea forrnaldehyde-bisulfite resins. .Thedissolved sjulfatej ion concentration. for best adsorption; ofthe'se --resins in most instances is within thefrang e of-aboutfZO toQlSO parts per -mil1ion,"a'ndparticularlyabout to 60 ,q

parts per million; Theoptim um sulfate ion concentrationyaries from resin to resin, andismost-conveniently determined byflaboratory trials as showri iu the Maxwell Y et 211, patent.

. N0 commerciall practical method exists atthe present time for exercising idiiect; control over the dissolved sulfate. ion;co'ntent' of papermaking"fibroussuspensions within'the limits mentioned. I It is' therefore' general ,practice" to bleed off'a portion of the whitewater from 3 closed-whitewater systems, replacing it "with fresh in;

an efiortto maintain the'dissolved sulfate 'ion'co'ntent of the water within desirably lowlimits. *This, however, 1 a I a usually does-not produce--optimuni results in open sys-. i

tems since'paper mill make-up Water is; generally fresh river and well wa'ters'which frequently contain substantial amounts of'dis'solve'd. sulfate ions, valuesof 1:01250 part's'per millibnheing common. Moreover, discharge of this water frequently. gives -rise 'to stream pollution problems and many event results in complete Waste of V the aluminum and sulfate ions dissolved therein. t e Furthermore, the whitewater contains'a PIOPQItiOH of cellulosic fiber i fine'sythat is, fibersgwhich are so small that they are not retained n the wire screenwh'en the fibrous suspension is' fsheeted j;These'fiber's are similarly lost when the white water is sent to waste.

' From the foregoing, it isv evident that the manufacture of rosin-sized fwet strength paper is'not now performed I generally under' optimum or most efficient conditions.

The discovery has now been made that dissolved sulfate barium base to the paper-making fibrous suspension after completion of the sizin operation, and aging. the suspension untila floc of. aluminum hydrate forms which adsorbsthe barium sulfateparticles also'preeipitated, there-i by im'proving the weight and opacity of the sheet. 'We haveifoundthat where the fibrous suspensions aretreated,

for. example, with 2% of rosin-size and 3% of alum, the. Weight of the paper obtained is increased by about 1.5

lbs. for every'poundl of barium' compound added."v According tothe invention, atleast sufiicient'of the barium base added to forma barium sulfate-precipitate and an aluminum hydrate flocas described, butinsufiicient to in-- crease the pH ofithe suspension above abo'ut,6. 'Within 7 Y Patented June 21,1955

and aluminum values in paper mill Whitewaters which; 1

these limits sufficient dissolved sulfate ions remain to rosin-sizing purposes, permitting the white water to be recycled. The amount of barium base added is therefore normally slightly less than the stoichiometrical equivalent of the aluminum sulfate r maining as excess from" th rosin sizing step, and therefore permits the water to be reused far more extensively than would otherwise be the case. The principal limit to reuse of the water is the accumulation of sulfate ions resulting from formation of sodium sulfate ions during the rosin-sizing step and the sulfate ions required to be present to give the necessary acidity.

A wet strength resin may be added if desired according to the invention at any point after the action of the added barium compound: is substantially complete, best results being obtained when the make-up water contains l ss than about 150 parts per million of dissolved sulfate ions, and the amount of added barium base is sufiicient to decrease the dissolved sulfate ion concentration to a value at which the resin is best adsorbed by the fibers.

From the foregoing, it will be apparent that the present invention may be described broadly as a method for manufacturing sized, filled paper which comprises forming asuspension of papermaking fiber in aper mill make-up water, sizing the fibers therein by addition of at least about /2% of rosin size and /4 of alum thereto, based on the dry Weight of the fibers, adding a watersoluble barium base in amount at least sufficient to precipitate barium sulfate particles and an aluminum hydrate fioc, but insufiicient to raise the pH of the suspension above about 6, aging the suspension until the floc of alurninunr hydrate adsorbs said barium sulfate particles and carries. them to the fibers, and sheeting and drying the fibers to form paper.

The invention is usefully applied in paper mills having open white water systems, that is, systems Where the whitewater is not recycled but is sent to waste. Because natural well or river waters generally contain 50 to 250 parts per million of dissolved sulfate ions, it is possible to deposit a substantial amount of the sulfate ions supplied by these waters on the cellulose fibers in addition to those introduced by the addition of alum, thus forming a heavier and more opaque paper while providing a mill effluent which has a decreased content of dissolved salts.

The invention is particularly adapted for use in mills which employ completely or substantially closed white water systems. According to the invention in this application, the fibrous suspension is most advantageously treated with sufficient of the barium compound to decrease the dissolved sulfate ion content to the value at which the particular wet strength resin. to be added is best adsorbed but with not so much as to raise the pH of the water above about 6.

An advantage of the present invention which is particularly evident in cyclic but not completely closed systems wherein rosin-sized wet strength paper is made is that it permits the dissolved sulfate ion concentration of the water to be maintained during extended reuse at a desirable low value for effective adsorption of the wet strength resin.

Calculations show that in a paper mill employing fresh make-up water containing 50 parts per million of dissolved sulfate ions, recirculating all its white water ina completely closed system, and manufacturing rosin-sized paper by adding 2% of liquid rosin size and 3% of alum to a cellulose suspension at 1% consistency, the white water reaches the maximum practical value of 800 parts per million of dissolved sulfate ions after it has been recycled about five times. Calculations further show that when this procedure is modified according to the present invention by the introduction of sufficient of a barium base during each cycle to decrease the dissolved sulfate ion concentration by 100 parts per million, the white water. may be recycled at least 15 times before a content 4. of 800 parts per millionof dissolved sulfate ions is reached.

In the practice of the process: of the present invention, any make-up water of the type generally used may be employed since paper. manufacturers normally avoid water containing more than; 250. parts per million of: dissolved sulfate ions.

As barium bases,. barium oxide and barium hydroxide are equally satisfactory and may be added in powdered or dissolved form. Although it has not been tried, there is no reason to doubt but that barium aluminate would not prove equally valuable, and is therefore included within the scope of the present invention.

The amount of the barium base added should be at least sufficient toprecipitate barium sulfate and aluminum hydrate floc. Only a small amount is needed to produce some benefit to the paper and the water, as the solubilities' of these materials are about 2.3 and 1 part per million respectively. At the other extreme, the amount of barium base should be limited so that, afterdevelopment of the fioc as described, the pH of the suspension is not in excess of about 6'. When a larger amount of the barium base is added so as to carry the pH of thesuspension to a materially higher value, an excess of sodium ions over sulfate ions develops resulting in poor adsorption of a subsequently-added wet strength resin or deficient size retention where the water is recycled. Within this range the amount of barium basemay be varied to precipitate desired amounts of barium sulfate and aluminum hydrate'fioc onthe fibers.

In practicing the invention, the stock after addition of the barium compound is aged for sufiicient time to allow complete development of the aluminumhydrate lice and adsorption of the finely-divided barium sulfate particles and cellulosic fines by the floc. Formation of fioc takes place rapidly but substantially complete development appears to require between about three minutes and ten minutes. For this purpose, the stock may be aged by storage or gentle stirring in the beater, or by pumping the suspension through a chest inwhich the suspension will have an average residence time about equal to the aging period. During this aging the floc adsorbs the barium sulfate particles and the cellulosic fines present and appears to carry them to the fibers.

The wet strength resin is added after action of the barium base is substantially complete and preferably is added by metering a solution thereof into the suspension at a point near the headbox.

As water-soluble barium bases suitable for the practice of the present invention, there may be employed barium oxide, barium hydroxide, barium aluminate, and known equivalents thereof. The materials may be added in solid form or dissolved in water.

The process of the present invention is applicable to all types of rosin size, including fortified rosin size, that is,

rosin size containing a minor amount of a size prepared. by Diels-Alder reaction of rosin with an unsaturated acid' such as maleic anhydride, soap sizes in general, and to rosin and soap size in combination with wax sizes'including emulsified asphalt sizes.

Any wet strength resin which would otherwise be ef-' fective may be employed according to the present invention, but the present invention is'particularly useful in connection with resins of U. S. Patent Nos. 2,345,543 and 2,559,221, and the anionic urea-formaldehyde bisulfite resins of U. S. Patent No. 2,582,840.

The sizing agents and wet strength resins employed together with themethods by which these materials are deposited on the fibers and the fibers are formed into paper or other cellulosic web are not particular features of the present invention.

The invention will be more particularly illustrated by the following examples. These examples are embodiments of the invention and are not to be construed in limitation. thereon.

the cationic melamine-formaldehyde" Example 1 2,000 lbs. of sulfite wood pulp are beaten at'0.6% consistency in water containing 60 parts per million of dissolved sulfate ions. This water is 80% recirculated white water recovered from the manufactureo'f rosin-sized paper. To this suspension are added 40 lbs. (dry basis) of liquid rosin size and 60 lbs. of papermakers alum. After all of the alum has been dispersed, 32 lbs. of powdered barium oxide are sprinkled in, and the suspension is discharged from the beater.

The suspension is aged for five minutes by flow through a large storage tank and is then refined and sheetedon a Fourdrinier machine in the usual manner. The product is paper composed of rosin-sized cellulose fibers carrying alumina hydrate floc having barium sulfate particles adplete,'and"sheeting andldrying the fibers toform' a cellulosic web.

I 2. Aprocessiaccordingito'claim l'whereinthe barium a base is barium hydroxide.

3.-.A processaccording to claim 1' wherein the base is barium-- alurninate.

4. A cyclic'methodfor manufacturing sized paper of 0 improved opacity. and weight while; inhibiting increase in the dissolved sulfate ion content of the "white water, whch comprises forming a suspension of papermaking cellulosic,

fibers, in recycled'paper mill water, sizing said fibers in said suspension by addition of about 1%.3% of rosin size and 1 /2% to 4 /2%. of alum thereto, adding a watersorbed thereon. The paper carries about 1.8% of barium sulfate and 0.4% of aluminum hydrate corresponding to about 80% retention of both of these materials.

The white water drainedv from the fibers during sheeting contains about 90 partsper million of dissolved sulwithout the addition of make-up water.

fate ions and is suitable for reuse in the process'described,

Example 2 a To the suspension in the beater To the stock at the headbox is added a dilute aqueous dispersion of the colloidal cationic melamine-aldehyde resin of U. S. Patent No. 2,345,543, generally known as Parez" Resin 607, at the rate of 2 lbs. of the resin per 100 lbs. of fibers, both calculated on the dry basis.

The paper formed is heated on rolls at-230 F. to dry the same and develop the strengthening properties of the wet strength resin thereon. The dry paper obtained is well-sized paper of normal resistance to penetrationby water and of normal wet strength; Itcontains about 2% of barium sulfate and 0.45% of aluminum hydrate corresponding to a 90% retention of both materials.

The white water containing60 parts per million of .disi

solved sulfate ions 'is suitable for recycling asdescribed..;;

From the foregoing, there is'reason to believe that an improvement can be effected by the useof barium chloride in conjunction with the barium'base, especially when the two materials are added inabout equimolecular propor tions. There is reason to believethat the use of the two materials in combination would permit, more extensive soluble barium 'base' selected from the] group consisting of barium hydroxide, barium oxide and barium aluminate i in an amount less than'the stoichiometri ca l equivalent of the excess of the aluminum. sulfate and at least sufi ficient to precipitate barium ion as barium sulfate and aluminum as an. aluminum hydrate floc butinsufiicient. to raise, the pH of the"suspension abovejabout .6, aging the suspension until development ofsaidfloc andadsorption f of said barium sulfate particles thereby are substantially complete, sheeting said fibers to formpaper while draining white water therefrom, maintaining the dissolved;

' sulfate ion concentration of said white water.;below about" 800 parts per million by addition .of waterfof low sulfate ion content thereto,.and recycling said white water; I

5." A method'according to claim 4,,'wherein a portion r of the whitewater is bledoifto maintain the qua tity of Wateriin the system substantially'coustant. 1

, 6. A cyclicf method for ,manufacturing sized, wet; strength paperof improved opacity and, weighfwhile 5 maintaining the dissolved sulfate ion content of the :water at a desirably low value dun'ngfadsorpti'ou offthe'i wet strength'resin, which comprises forming a suspension of papermaking cellulosic fibers in substantially' recycIed paper mill water-having a dissolved sulfate ion content of," j about 104120 partsp'er million, s'izing'said fibers-in said suspension .by'addition 'of-"at"least- /2'% ,to about 13% of: rosin size and toabout 4 /2 jofpapermak'ers" alum thereto, based on the. dry weight of the fibers, ,addingfa 2' 1 Water-soluble barium base selected from; the groupfconf; sisting of barium hydroxide, bariumoxide" and, barium aluminate "in anfamoun't .less than the lstoich'iome trical equivalent of the excess of the aluminumsulfate "and ;at; leastsuflicient toprecipitate, aluminum as. an; aluminum f hydrate-floc andbariurn ionsias barium isulfate "particles,

but insufiicient toY-increasefthe'; pH of the" suspension :to above about; 6', thereby also decreasing fthe dissolved sulfa'teiion concentrati'on to a* value at which the fw'e t 4 strength resin to be addedis. best adsorbed by'the fibers,

, aging thefsuspension until the {floc of aluminur'nhydrate adsorbs saidbarium sulfateparticles', adding an aqueous solution of'a cellulose-substantive wet strength'r'esinand I precipitation of sulfate ions while providing s'uflicient acidity through the aluminum sulfateequivalent which would remain.

I claim:

1. A method for manufacturing sized cellulosic webs.

adsorbing the same on the fibers,,[sheeting.said,fibers to form paper. while drainingjwhitewatertherefrom, main- I tainingfthe'dissolved sulfate ion concentration of said --white water below-150 parts per million by addition of Water of low dissolvedioncontent thereto, andrecycling of improved opacity and weight, which comprises forming a suspension of papermaking cellulose fibers in paper mill make-up water, sizing said fibers in said suspension by addition of at least 14% to about 3% of rosin size and 4% to about 4 /2% of alum thereto, based on the .dry weight of the fibers, adding a water-soluble barium base selected from the group consisting of barium hydroxide, ba1ium oxide and barium, aluminate in an amount less than the stoichiometrical equivalent or the excess of the aluminum sulfate and at least sufiicient to precipitate said .white water.

7. Aprocess accordingto'claim 6 wherein, a portion I of the white waterpis bled olf to maintain the quantity;

1 of water in the system substantiallyconstant;

barium ion as barium sulfate ,and aluminum as an aluminum hydrate floc but insufiicient'to raisethe. pH

of the suspension above about 6, aging the. suspension until development of said floc and adsorption of said barium sulfate particles thereby are substantially ,com-

a UNITED STATES PATENTS. I p ,L15 7,198 {DuenilingQ, 1;; Nov. 24, 1874- 1,317, 19, *DeCe'w rseptso, 1919 2,315,892 Booth -.Apr. 6,, 1 943 5 2,559,221 Maxwell al'. July 3,1951 2,599,093 :Craig 'j ,June 3,1952, 7

References Cited in the file of thispatent l-OTHERREFEREN 's-i Dohne et al.: Paper Trade I November .27, 1941, 

1. A METHOD FOR MANUFACTURING SIZED CELLULOSIC WEBS OF IMPROVED OPACITY AND WEIGHT, WHICH COMPRISES FORMING A SUSPENSION OF PAPERMAKING CELLULOSE FIBERS IN PAPER MILL MAKE-UP WATER, SIZING SAID FIBERS IN SAID SUSPENSION BY ADDITION OF AT LEAST 1/2% TO ABOUT 3% OF ROSIN SIZE AND 3/4% TO ABOUT 41/2% OF ALUM THERETO, BASED ON THE DRY WEIGHT OF THE FIBERS, ADDING A WATER-SOLUBLE BARIUM BASE SELECTED FROM THE GROUP CONSISTING OF BARIUM HYDROXIDE, BARIUM OXIDE AND BARIUM ALUMINATE IN AN AMOUNT LESS THAN THE STIOCHIOMETRICAL EQUIVALENT OF THE EXCESS OF THE ALUMINUM SULFATE AND AT LEAST SUFFICIENT TO PRECIPATE BARIUM ION AS BARIUM SULFATE AND ALUMINUM AS AN ALUMINUM HYDRATE FLOC BUT INSUFFICIENT TO RAISE THE PH OF THE SUSPENSION ABOVE ABOUT 6, AGING THE SUSPENSION UNTIL DEVELOPMENT OF SAID FLOC AND ADSORPTION OF SAID BARIUM SULFATE PARTICLES THEREBY ARE SUBSTANTIALLY COMPLETE, AND SHEETING AND DRYING THE FIBERS TO FORM A CEILULOSIC WEB. 